Machine for polishing optical surfaces



y 9, 1956 P. ANGENIEUX 2,747,340

MACHINE FOR POLISHING OPTICAL SURFACES Filed Nov. 8, 1952 2 Sheets-Sheet l \IPAS 13 (Q Q Mk 1 i L I INVEHTORZ PIERRE Alyssmsux BY:

May 29, 1956 P. ANGENIEUX 2,747,340

MACHINE FOR POLISHING OPTICAL SURFACES Filed Nov. 8, 1952 2 Sheets-Sheet 2 INVEHIOR'. PIERRE AHGEHIE UK United States Patent O MACHINE FOR POLISHING OPTICAL SURFACES Pierre Angnieux, Paris, France Application November 8, 1952, SerialNo. 319,575

Claims priority, application France Novemberll, 1951 2 Claims. (Cl. 51-124) This invention relates to machines of the kind used for polishing curved optical surfaces and its essential scope is to improve the efficiency of these machines and to obtain a higher degree of accuracy.

It is known that the machines designed for polishing spherical optical surfaces comprise on the one hand a block member on which the parts to be polished (as a rule, lenses) are fixed and, on the other hand, a polishing member engaging the parts to be polished, both the block member and the polishing member having imparted there to a given motion in view of varying their relative positions while maintaining the operative engagement between the polishing member and the parts to be polished. Generally the lower element (polishing member of block) which is the element having a convex surface is rotatably driven about its axis of symmetry whilst the other element, having a concave surface, is disposed above the former and caused to oscillate.

It is the object of this invention to provide a machine wherein it is the element having a convex surface that is caused to oscillate about an axis passing through the center of curvature which is common to both spherical surfaces. Experience teaches that with this arrangement the time required for a polishing operation is reduced and the accuracy of the work improved.

Thus, the machine according to the invention comprises two elements each formed with a spherical surface and constituted the one by a polishing member and the other by the surfaces to be polished, and so located that these spherical surfaces, which have a same curvature, one surface being convex and the other concave, engage each other, means for impressing to the element having a convex surface an oscillatory motion about an axis passing through the center of curvature common to both surfaces, each element being rotatably mounted about an axis corresponding substantially to its axis of symmetry and passing through the common center of curvature of both spherical surfaces, and means for positively driving for rotation about its axis one of these elements, which may be either the convex-surfaced or the concave-surfaced element of the two.

Preferably, the element having a concave spherical surface has its axis of rotation held in a substantially fixed position by means of a ball-pivot.

A form of embodiment of the machine according to the invention is described hereafter with reference to the attached drawings, it being understood that the characteristic features resulting from the description and the drawings are part of the invention. In the drawings:

Figs. 1 to 3 illustrate three different positions of a form of embodiment of the machine according to the invention;

Figs. 4 and 5 are more detailed views, in elevation and longitudinal section respectively, of the form of embodiment illustrated in Figs. 1 to 3.

The drawings illustrate on the one hand an element 1 having a concave spherical surface 1a and acting as a 2 ,747,340 Patented May 29, 1956 polishing member, and on the other hand an element 2 constituting a supporting block for lenses such as 3 of which the convex surface 3a is to be polished. The block member 2 is adapted to be imparted on the one hand a rotary motion about its axis of symmetry 4 and, on the other hand, an oscillatory motion about an axis at right angles to the plane of the figure and passing through the center of curvature 5 common to both surfaces In and 3a. Figures 1 and 3 show the block 2 in the endmost positions of its oscillatory movement whilst Figure 2 shows the same block in its intermediate position. The polishing member 1 is merely held in engagement with the parts 3 to be polished by a ball-shaped joint member of ball-pivot 6 secured endwise of a shaft 7 adapted to slide in its longitudinal direction and coaxial with the polishing member. Thus, the latter is able completely to fit on the spherical surface of the parts 3 and to rotate about its axis of symmetry.

A device of this kind wherein the shaft 7 is vertical and the polishing member 1 positioned above the block member 2 is advantageous in that the resultant of the pressures exerted by this polishing member 1 on the block member 2, on account of the weight of the former, is constant both in direction and strength; however, it is obvious that the device may be directed otherwise, in which case the polishing member would be urged against the block member by a spring.

in the foregoing, the case of convex surfaces to be polished is contemplated but it will occur to anybody skilled in the art that in case of concave surfaces to be polished the relative positions of the block member to be polished and the polishing member must be reversed, i. e. the element 1 acting as a support for the parts to be polished and the other element 2 as the polishing member.

In Figs. 4 and '5 a frame structure 8 having mounted therein a horizontal shaft 9 is shown. On this shaft is mounted for rocking motion a strap member 10 operatively connected atone end to a link 11 driven by a wheel 12; the latter .is keyed on a shaft 13 adapted to be rotatably driven through any suitable means. Another shaft 14 having its axis at right angles to that of shaft 9 is rotatably mounted in a bearing 15 fitted in the other arm of the strap member 10. On this shaft 9 is keyed a bevel wheel 16 in peripheral driving engagement with another bevel wheel 17 keyed on shaft 14. Both wheels 16 and 17 constitute a couple of angle wheels and the driving of one wheel by the other may occur either by simple frictional engagement or by meshing engagement, in which case both wheels are provided with teeth. On the shaft 14 is mounted the block member 2 on which are fixed the surfaces to be polished whilst the polishing member 1 is simply held in engagement with this block member 2 through the medium of a ball-shaped joint element 6 provided at the bottom end of a shaft 7 mounted for free sliding movement in a bore provided in the upper arm 8a of the frame. The pressure exerted by the polishing member 1 on block member 2 may be adjusted by means of a weight 18 secured at the upper end of shaft 7. The polishing member 4 has a concave shape and the surfaces to be polished are convex if co'ncave surfaces are to be polished, the relative positions of the block member to be polished and the polishing member must be reversed, as already indicated hereabove. The common center of the polishing member and of the surfaces to be polished is normally at 19, where the axes of shafts 9 and 14 intersect each other, but an adjusting nut 20 makes it possible to vary the position of this center if need be, notably in view of restoring the desired curvature to an assembly of surfaces to be polished diverging therefrom.

When the shaft 13 is actuated it drives the wheel 12 and the link 11 imparts an oscillatory motion to the strap member which is adjustable in amplitude on account of the adjustable mounting of the trunnion 21 secured on the strap member 10. The wheel 17 fast with the block memher 2 is thus imparted the oscillatory motion and acts as a follower relative to the driving wheel 16. The shaft 9 on which this wheel 16 is keyed may be either held against motion or rotatably driven, at will. If it is held against rotation the wheel 16 remaining stationary the other wheel 17 will be caused to rotate about its axis on account of the oscillatory motion of this axis about the axis of shaft 9, the direction of this rotary motion changing with that of the oscillatory movement. Thus, the block member 2 fast with wheel 17 will be imparted two different motions, namely an oscillatory motion about the axis of shaft 9 and an alternating rotary motion about its axis of symmetry. If a rotary drive is impressed to shaft 9, the velocity of rotation of the block 2 about its axis of symmetry is changed, that is, it is increased during one half-cycle of the oscillatory motion and reduced during the other half-cycle. If the velocity of rotation of shaft 9 relative to that of the wheel 12 controlling the oscillatory motion is high enough, the rotary motion of the block member 2 about its axis of symmetry will remain unchanged as far as its direction of rotation is concerned; it is a continuous motion and its velocity will remain variable during the complete cycle. Thus, if adequate variable-speed drive means are provided for both shafts 9 and 13, an infinite ratio may be provided between the velocities of the oscillatory motion and rotary motion applied to the block member 2.

An extremely simple machine may be constructed by securing to the frame the aforesaid shaft 9 and therefore the wheel 16 fast therewith. As already disclosed hereabove the rotary motion of block member 2 is converted into a reciprocating motion; the polishing action is effected in very. good conditions both in accuracy and in efficiency, a favorable effect being derived from this alternating form of motion.

The above description is given merely by way of example in order to illustrate in a concrete manner the principle of the invention. It is obvious that the arrangeat right angles to the common axis of symmetry of said concave and convex spherical elements and passing through their common centre of curvature, said arm being underslung so as to support said convex element through the medium of a shaft coaxial with the axis of symmetry of said convex element and so mounted as to be rotatable about said arm, power means for oscillating said arm together with the convex element supported thereby, a first transmission wheel keyed on the shaft of said convex ele' ment, another transmission wheel in meshing engagement with said first wheel and coaxial with the axis of oscillation of said oscillating arm, said other transmission wheel being fixed with respect to said supporting frame,

whereby the movement of rotation transmitted to said convex element about its axis of symmetry is of alternating character and of the same velocity in one and the other direction.

2. Machine for polishing spherical optical surfaces comprising a supporting frame, a concave spherical element constituting the polishing tool and a convex spherical element of same centre of curvature and same axis of symmetry as said concave element, which consists of the optical surfaces, said convex element being disposed within and in engagement with said concave element, said concave element resting freely on said convex element, a pivot pin provided with a spherical extremity and guided in said supporting frame, the axis of symmetry of said pivot pin passing through the common centre of curvature l having impressed thereto an oscillatory movement about an axis at right angles to the common axis of symmetry of said concave and convex spherical elements and passing through their common centre of curvature, said arm being underslung so as to support said convex element through ment of the various parts may be modified, and that,

notably, the vertical arrangement of the axis of symmetry of the assembly, although particularly advantageous, may be modified and given a different orientation without departing from the spirit and scope of the invention.

What I claim as new is:

1. Machine for polishing spherical optical surfaces comprising a supporting frame, a concave spherical element constituting the polishing tool and a convex spherical element of same centre of curvature and same axis of symmetry as said concave element, which consists of the optical surfaces, said convex element being disposed within and in engagement with said concave element, said concave element resting freely on said convex element, a pivot pin provided with a spherical extremity and guided in said supporting frame, the axis of symmetry of said pivot pin passing through the common centre of curvature of both elements, said concave element being mounted for free rotation about said pivot pin under the influence of the friction resulting from the movements of said convex ele ment, an arm carried by said supporting frame and having impressed thereto an oscillatory movement about an axis the medium of a shaft coaxial with the axis of symmetry of said convex element and so mounted as to be rotatable about said arm, power means for oscillating said arm together with the convex element supported thereby, a first transmission wheel keyed on the shaft of said convex element, another transmission wheel in meshing engagement with said first wheel and coaxial with the axis of oscillation of said oscillating arm, said other transmission wheel being driven for rotation about its axis, whereby the movement of rotation transmitted to said convex element about its axis of symmetry is of alternating character and of different velocity in one and the other direction.

References Cited in the file of this patent UNITED STATES PATENTS 

